High security environments exist wherein the area to be secured is essentially a room within a building. Typically, ingress into the secured area is by a pedestrian door. The overall security of the secured area depends upon the door staying in a locked condition by a highly secure lock at all times whenever the pedestrian door is not open.
Whenever a combination lock/deadbolt lock such as a Mas-Hamilton Group CDX-07 is used to provide the security to the pedestrian passage, the security against unauthorized entry is highly effective; however, the deadbolt does not permit ready egress in emergency situations. Both the deadbolt must be manually retracted by turning a knob and the door latch operated, usually necessitating a two-handed operation to open the door from the inside. In circumstances where an emergency requires unimpeded egress, such as a fire or toxic gas leak, it is undesirable to require the use of two hands, and two motions to operate the securing devices in order to exit the secured area through the pedestrian passage. Some regulatory agencies and states require the securing devices on at least some doors be operable with only a single motion.
Additionally, it is desirable to provide a method permitting egress from the secured area through the pedestrian passage without the need to grasp any device, such as a knob, handle, or lever. It is common to install a push-to-open door latch device for such situations. Such a device also is commonly referred to as a panic-bar or panic-bar device. A panic-bar device is operated by a force pushing on the bar or touch bar which then activates and withdraws the latchbolt which had secured the door in its closed position.
Seeking to exit a room in an emergency, the natural action of a person is to extend a hand and push on the door to cause it to swing outward. Doors for emergency exits are required by fire, safety, or building codes to open outwardly, not to obstruct egress in an emergency. Even if the person trying to exit in an emergency situation reached toward the push-bar or panic-bar device and missed it, other body actions such as by hip pressure usually will be adequate to cause the panic-bar device to operate to withdraw the latchbolt which is holding the door in its secured condition.
However, wherever a deadbolt lock of the Mas-Hamilton Group CDX-07 type is used to render the enclosure highly secure, operation of the panic-bar device will not permit opening the pedestrian door without the use of a hand to operate the knob controlling the deadbolt withdrawal. The CDX-07 deadbolt lock and similar locks include a combination dial lock which provides the locking function while the deadbolt portion permits the door to be closed and the deadbolt extended to secure the door. The combination lock must be operated to withdraw the deadbolt from outside the door of the secured area.
A prior attempt to solve this severe problem was the panic-bar exit used with the Sergeant and Greenleaf Model 8470 combination lock/deadbolt. This device is described in Walter R. Evans U.S. Pat. No. 4,961,330.
A panic-bar mechanism of a different design is manufactured and sold by NT Monarch Hardware under a designation of Push-Bar Series 18 Exit Devices. Such push-bar devices are available from NT Monarch Hardware of Shepherdsville, Ky. 40165. While the NT Monarch Push-Bar Exit Devices are very adequate for maintaining a door in a latched position and permitting emergency egress, the operation of the panic-bar still is incapable of operating a combination lock with a deadbolt such as the Mas-Hamilton CDX-07.
The panic-bar of Walter R. Evans, described in U.S. Pat. No. 4,961,330, is operated from the interior by pushing the push-bar which acting through a rigid linkage operates the deadbolt to withdraw the bolt. Ingress to the secured area is accomplished by dialing and operating the combination lock to withdraw the deadbolt and by operating a device, such as an electronic lock control, to provide a signal to further operate the panic-bar latch thereby withdrawing the latchbolt. The electronic signal controlled panic-bar latch control is disposed to pull the latchbolt but relies on a one-way drive connection in the chain of elements between the push-bar and the latchbolt to withdraw the latchbolt but not to effect the chain of elements activated by push bar operation that could act to withdraw the deadbolt.